1. Field of the Invention
The present invention relates to substrates provided with a photocatalytic coating, to the process for obtaining such a coating and to its various applications.
It relates more particularly to coatings comprising semiconducting materials based on metal oxides, especially titanium oxide, which are capable, under the effect of radiation of suitable wavelength, for initiating radical reactions causing the oxidation of organic substances.
The coatings thus allow the materials that they coat to be given new functionalities, especially anti-soiling, fungicidal and bactericidal properties, these optionally being combined with hydrophilic properties, antifogging properties, optical properties, etc.
Very diverse substrates may be envisioned, especially those used in the field of vehicles or buildings, such as glazing and curtain wall, cladding, roofing or floor materials, such as tiles, slates, slabs, tiling and more generally any material used in construction. These materials may thus be made of glass, metal, glass-ceramic, ceramic, cement, brick, wood, stone or material reconstituted from these natural materials, of plastic or, fibrous material of the mineral wool type, especially for filtration processes, etc.
They may also be classified as transparent materials, used in particular in glazing, such as glass or flexible or rigid plastic substrates, such as substrates made of a polyester or of an acrylate like polymethyl methacrylate (PMMA). The substrates may also be classified in the category of non-porous or slightly porous materials (glass) or in the category of (relatively) porous materials, such as tiles and ceramics.
The substrates may be regarded as “mono-materials” such as glass substrates, or substrates comprising a superposition of materials, or layers, such as curtain walls provided with a coating of the curtain wall render type.
2. Description of the Prior Art
Already known, from international patent applications WO 97/10186 and WO 97/10185 are coatings containing anatase-crystallized TiO2 having photocatalytic properties, these coatings being obtained from the thermal decomposition of suitable organometallic precursors and/or from “precrystallized” TiO2 particles encapsulated in a mineral or organic binder.
Also known, from patent WO 99/44954 is an improvement to these types of coatings consisting in the use of precrystallized TiO2 particles encapsulated in a binder which also contains partially crystallized TiO2: the binder thus participates in the photocatalytic effect of the particles, enhancing the performance of the coating both in terms of photocatalytic properties and durability properties.
Also known, from patent applications EP-1 036 826 and EP-1 081 108, are coatings using TiO2 particles in a binder containing zirconium oxide.